From: Greg Kroah-Hartman Date: Mon, 4 Feb 2019 06:04:03 +0000 (+0100) Subject: 4.4-stable patches X-Git-Tag: v4.20.7~23 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b758de3869ae56f44cf19c6ace0784182bdb37cd;p=thirdparty%2Fkernel%2Fstable-queue.git 4.4-stable patches added patches: kernel-exit.c-release-ptraced-tasks-before-zap_pid_ns_processes.patch mm-oom-fix-use-after-free-in-oom_kill_process.patch --- diff --git a/queue-4.4/kernel-exit.c-release-ptraced-tasks-before-zap_pid_ns_processes.patch b/queue-4.4/kernel-exit.c-release-ptraced-tasks-before-zap_pid_ns_processes.patch new file mode 100644 index 00000000000..2baf1d6ab56 --- /dev/null +++ b/queue-4.4/kernel-exit.c-release-ptraced-tasks-before-zap_pid_ns_processes.patch @@ -0,0 +1,73 @@ +From 8fb335e078378c8426fabeed1ebee1fbf915690c Mon Sep 17 00:00:00 2001 +From: Andrei Vagin +Date: Fri, 1 Feb 2019 14:20:24 -0800 +Subject: kernel/exit.c: release ptraced tasks before zap_pid_ns_processes + +From: Andrei Vagin + +commit 8fb335e078378c8426fabeed1ebee1fbf915690c upstream. + +Currently, exit_ptrace() adds all ptraced tasks in a dead list, then +zap_pid_ns_processes() waits on all tasks in a current pidns, and only +then are tasks from the dead list released. + +zap_pid_ns_processes() can get stuck on waiting tasks from the dead +list. In this case, we will have one unkillable process with one or +more dead children. + +Thanks to Oleg for the advice to release tasks in find_child_reaper(). + +Link: http://lkml.kernel.org/r/20190110175200.12442-1-avagin@gmail.com +Fixes: 7c8bd2322c7f ("exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()") +Signed-off-by: Andrei Vagin +Signed-off-by: Oleg Nesterov +Cc: "Eric W. Biederman" +Cc: +Signed-off-by: Andrew Morton +Signed-off-by: Linus Torvalds +Signed-off-by: Greg Kroah-Hartman + +--- + kernel/exit.c | 12 ++++++++++-- + 1 file changed, 10 insertions(+), 2 deletions(-) + +--- a/kernel/exit.c ++++ b/kernel/exit.c +@@ -450,12 +450,14 @@ static struct task_struct *find_alive_th + return NULL; + } + +-static struct task_struct *find_child_reaper(struct task_struct *father) ++static struct task_struct *find_child_reaper(struct task_struct *father, ++ struct list_head *dead) + __releases(&tasklist_lock) + __acquires(&tasklist_lock) + { + struct pid_namespace *pid_ns = task_active_pid_ns(father); + struct task_struct *reaper = pid_ns->child_reaper; ++ struct task_struct *p, *n; + + if (likely(reaper != father)) + return reaper; +@@ -471,6 +473,12 @@ static struct task_struct *find_child_re + panic("Attempted to kill init! exitcode=0x%08x\n", + father->signal->group_exit_code ?: father->exit_code); + } ++ ++ list_for_each_entry_safe(p, n, dead, ptrace_entry) { ++ list_del_init(&p->ptrace_entry); ++ release_task(p); ++ } ++ + zap_pid_ns_processes(pid_ns); + write_lock_irq(&tasklist_lock); + +@@ -557,7 +565,7 @@ static void forget_original_parent(struc + exit_ptrace(father, dead); + + /* Can drop and reacquire tasklist_lock */ +- reaper = find_child_reaper(father); ++ reaper = find_child_reaper(father, dead); + if (list_empty(&father->children)) + return; + diff --git a/queue-4.4/mm-oom-fix-use-after-free-in-oom_kill_process.patch b/queue-4.4/mm-oom-fix-use-after-free-in-oom_kill_process.patch new file mode 100644 index 00000000000..66afa1b27e3 --- /dev/null +++ b/queue-4.4/mm-oom-fix-use-after-free-in-oom_kill_process.patch @@ -0,0 +1,70 @@ +From cefc7ef3c87d02fc9307835868ff721ea12cc597 Mon Sep 17 00:00:00 2001 +From: Shakeel Butt +Date: Fri, 1 Feb 2019 14:20:54 -0800 +Subject: mm, oom: fix use-after-free in oom_kill_process + +From: Shakeel Butt + +commit cefc7ef3c87d02fc9307835868ff721ea12cc597 upstream. + +Syzbot instance running on upstream kernel found a use-after-free bug in +oom_kill_process. On further inspection it seems like the process +selected to be oom-killed has exited even before reaching +read_lock(&tasklist_lock) in oom_kill_process(). More specifically the +tsk->usage is 1 which is due to get_task_struct() in oom_evaluate_task() +and the put_task_struct within for_each_thread() frees the tsk and +for_each_thread() tries to access the tsk. The easiest fix is to do +get/put across the for_each_thread() on the selected task. + +Now the next question is should we continue with the oom-kill as the +previously selected task has exited? However before adding more +complexity and heuristics, let's answer why we even look at the children +of oom-kill selected task? The select_bad_process() has already selected +the worst process in the system/memcg. Due to race, the selected +process might not be the worst at the kill time but does that matter? +The userspace can use the oom_score_adj interface to prefer children to +be killed before the parent. I looked at the history but it seems like +this is there before git history. + +Link: http://lkml.kernel.org/r/20190121215850.221745-1-shakeelb@google.com +Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com +Fixes: 6b0c81b3be11 ("mm, oom: reduce dependency on tasklist_lock") +Signed-off-by: Shakeel Butt +Reviewed-by: Roman Gushchin +Acked-by: Michal Hocko +Cc: David Rientjes +Cc: Johannes Weiner +Cc: Tetsuo Handa +Cc: +Signed-off-by: Andrew Morton +Signed-off-by: Linus Torvalds +Signed-off-by: Greg Kroah-Hartman + +--- + mm/oom_kill.c | 8 ++++++++ + 1 file changed, 8 insertions(+) + +--- a/mm/oom_kill.c ++++ b/mm/oom_kill.c +@@ -544,6 +544,13 @@ void oom_kill_process(struct oom_control + * still freeing memory. + */ + read_lock(&tasklist_lock); ++ ++ /* ++ * The task 'p' might have already exited before reaching here. The ++ * put_task_struct() will free task_struct 'p' while the loop still try ++ * to access the field of 'p', so, get an extra reference. ++ */ ++ get_task_struct(p); + for_each_thread(p, t) { + list_for_each_entry(child, &t->children, sibling) { + unsigned int child_points; +@@ -563,6 +570,7 @@ void oom_kill_process(struct oom_control + } + } + } ++ put_task_struct(p); + read_unlock(&tasklist_lock); + + p = find_lock_task_mm(victim); diff --git a/queue-4.4/series b/queue-4.4/series index 9b184aba36e..fad042ec6ed 100644 --- a/queue-4.4/series +++ b/queue-4.4/series @@ -47,3 +47,5 @@ gfs2-revert-fix-loop-in-gfs2_rbm_find.patch platform-x86-asus-nb-wmi-map-0x35-to-key_screenlock.patch platform-x86-asus-nb-wmi-drop-mapping-of-0x33-and-0x.patch mmc-sdhci-iproc-handle-mmc_of_parse-errors-during-probe.patch +kernel-exit.c-release-ptraced-tasks-before-zap_pid_ns_processes.patch +mm-oom-fix-use-after-free-in-oom_kill_process.patch